target/linux/bcm53xx/patches-4.14/081-spi-bcm-qspi-switch-back-to-reading-flash-using-smal.patch

   1 From 940ec770c295682993d1cccce3081fd7c74fece8 Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
   3 Date: Thu, 11 Oct 2018 09:42:17 +0200
   4 Subject: [PATCH] spi: bcm-qspi: switch back to reading flash using smaller
   5  chunks
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 Fixing/optimizing bcm_qspi_bspi_read() performance introduced two
  11 changes:
  12 1) It added a loop to read all requested data using multiple BSPI ops.
  13 2) It bumped max size of a single BSPI block request from 256 to 512 B.
  14
  15 The later change resulted in occasional BSPI timeouts causing a
  16 regression.
  17
  18 For some unknown reason hardware doesn't always handle reads as expected
  19 when using 512 B chunks. In such cases it may happen that BSPI returns
  20 amount of requested bytes without the last 1-3 ones. It provides the
  21 remaining bytes later but doesn't raise an interrupt until another LR
  22 start.
  23
  24 Switching back to 256 B reads fixes that problem and regression.
  25
  26 Fixes: 345309fa7c0c ("spi: bcm-qspi: Fix bcm_qspi_bspi_read() performance")
  27 Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
  28 Signed-off-by: Mark Brown <broonie@kernel.org>
  29 Cc: stable@vger.kernel.org
  30 ---
  31  drivers/spi/spi-bcm-qspi.c | 2 +-
  32  1 file changed, 1 insertion(+), 1 deletion(-)
  33
  34 --- a/drivers/spi/spi-bcm-qspi.c
  35 +++ b/drivers/spi/spi-bcm-qspi.c
  36 @@ -88,7 +88,7 @@
  37  #define BSPI_BPP_MODE_SELECT_MASK              BIT(8)
  38  #define BSPI_BPP_ADDR_SELECT_MASK              BIT(16)
  39
  40 -#define BSPI_READ_LENGTH                       512
  41 +#define BSPI_READ_LENGTH                       256
  42
  43  /* MSPI register offsets */
  44  #define MSPI_SPCR0_LSB                         0x000